Roof Space Air Quality - Filters | Blog | Unovent

Roof Space Air Quality - Filters

23 November 2015
Roof Space Air Quality - Filters Roof Space Air Quality - Filters Blog

A common perception is that the air in the roof space of a home is very dusty. It’s also one of the most common questions we are asked  – “Won’t the air in the roof cavity be dusty and unhealthy?" The short answer is no.

The roof space of houses are designed to be well ventilated to the outside air. In fact, the air is changed every few hours so it’s fresh and ideal to be used for home ventilation. Surprisingly, it’s likely to be cleaner than the air outside. While the air is changed regularly, airborne particles are not easily blown through the small gaps into the roof space.

Think about it. When you look up into the ceiling space there is some dust on the horizontal surfaces but if you shine a torch around it will not show dust in the air. Given this space has never been cleaned since the house was built, isn’t this surprising? It’s almost certain if you live in a 40 year old home and didn’t dust the lounge in all that time, the dust would be much thicker.

At Unovent we decided to do a basic, easily understood experiment in an effort to understand this phenomenon better and be able to reassure customers that the air they are bringing into their home is very suitable for healthy ventilation.  

We fitted two Unovent ventilators side by side in the same room. One was fitted normally, bringing filtered air down from the roof space. The other was fitted upside down taking air from the room and venting it up into the roof space. Both are fitted with the industry standard G4 filter.

After 6 months the filters were removed for inspection. Two things were immediately apparent:

1.    The G4 filters have performed exceptionally well. The side exposed to the raw air is surprisingly soiled indicating that the particles are being trapped as the filter is designed to do. The exit side of the filter is slightly discoloured indicating that only a small proportion of particles (those smaller than the G4 design criteria – down to 10 um (Micron) which includes pollen, hairs spray, moulds, etc.), are reaching that surface.

2.    The filter in the ventilator fitted upside down – taking air from inside the room - is considerably more soiled than the filter fitted cleaning air being drawn down from the ceiling space normally. The evidence is clear; the air inside the home is more polluted than the air in the roof space. We believe this will be typical of every home.

The traditional method of airing a home is to open doors and windows. While we agree that this is very effective and certainly airs a home very well, conditions are not always suitable to enable this to be done. If the occupants of the house are away during the day it’s unlikely the doors and windows will be open for obvious reasons. An Unovent ventilation system will work automatically whenever the air conditions in the roof space are suitable resulting in year round ventilation.


The pictures clearly show the difference.  Fitting a Unovent home ventilation system will provide a suitable source of clean fresh air that will keep your home dryer, warmer and healthier.